The present invention is described in the context of a wind farm used for electric power generation but is applicable to numerous types of power generation systems including, for example, systems which generate electricity from solar cells and systems which generate electric power from wave energy. A feature common to these and other sources of green power is that the power output fluctuates, e.g., based on weather conditions. Yet it is desirable to integrate outputs from these sources with outputs from other electric power systems in a network. The network may be for the use of a local utility or part of a regional or even larger electric transmission network from which the power is distributed. It is desirable to find ways to improve the manner in which fluctuating power outputs, such as those resulting from some green power sources, are provided to lines which receive power from multiple sources.